Conventionally, in a SiC semiconductor device, a semiconductor element is divided into a main cell and a sense cell, and a current flowing in the main cell is detected by the sense cell. In this SiC semiconductor device, by forming an element isolation layer between the main cell and the sense cell, while appropriately performing element isolation between them, the electric field concentration below the element isolation layer is relaxed, and the main cell and the sense cell do not conduct to each other.